The Biostatistics Core serves as the resource for biostatistical and data management services for the Program Project. These resources can be grouped into the following areas of responsibility: 1) Biostatistical consultation including: planning of new studies, with regard to design, estimation of study size requirements, methods for randomization where appropriate and plans for statistical analysis; monitoring of current studies, statistical analysis and scientific reporting of study results; 2) Management of the dedicated computer, including computer systems for data storage and access, development of systems improvements, computer space management, computer administration, trouble shooting, collaboration in report development and collaboration in training of data managers, investigators and other personnel; 3) Data collection and management for current studies and development of plans for data collection for new studies, including forms design and modification where needed, procedures for entering and tracking patients, randomization of treatment assignments and aid in accessing data for monitoring studies in process and reporting of study results; 4) Procedures for assuring quality of the data collected and production of management reports for administrative and scientific administration, patient accrual, patient status, quality of the data, work progress in tracking patient and special reports requested by investigators; 5) Data management and biostatistical aid in assembling, summarizing and analysing data for scientific reports for seminars, national and international meetings and for publication in scientific journals. The Biostatistical Core has an established team in place. Computer and data systems have been developed and are operational for fulfilling the missions described above. The team is composed of a Principal Investigator, Biostatistician and Systems Manager (all Ph.D.'s experienced in planning and analyzing clinical trials) and a Data Manager Supervisor who supervises four data managers (one supported by the Program Project itself, the other three by the Stanford University Hospital).